Flea problem?

My puppy went to an (unknowingly) flea infested home over the weekend. About 3 weeks ago we gave him a spot on treatment which worked pretty well. He was nearly flea free. After this weekend he is crawling with them. Yesterday we tried a flea collar and it didn't work. Today he got his puppy first puppy shot. Would it be safe to spray him with flea spray? I feel terrible for the sweet boy, he is very itchy. 
Update: I also gave him a flea bath yesterday. 

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